I have this knoking sound when the engine is cold, I can not locate it. It seems to be louder underneath the car. It usually gets much better in a minute or so. This is not the hair dryer type sound that's suppose to be from the SAI pump and it is much louder than the fine ticking, when I get intermittently when the engine is warm.

It almost sound like an exhaust leak.
Could it be that the exhaust is leaking and when things warms up it stops?
I can not feel for the leak in the engine bay/manifold area, since the fun runs and I don't really know why the fun starts running at start up even when the outside temprature is freezing.

 

1. Two fans, one is mechanical, driven by the serpantine belt, and has a fan clutch that simply makes it run at low power or higher power, but never "no power". This type of clutch is called a viscous clutch, and is fully engaged when parked overnight and cold, becasue the silicone liquid inside has all pooled to one side. When engine cranks the fan will "roar" until clutch fluid warms up and spreads out by rotating force, and clutch backs off engagement to lower power option. You could remove the serpantine belt and crank the truck cold, to eliminate the fan motion. OK to run without fan as long as you don't stay parked or stopped for more than 3-5 minutes while testing. Some owners in the border states (Canadian border) run with no fan in the winter to warm up truck faster, just watch temp gauge when you are sitting for long periods).

2. Second fan is electric, and mounted on front of AC condenser. In D2 the ECU deides when to run this, and normally that is when truck is 212F coolant or above.

3. The knocking noise could be your engine operating with very low oil pressure, becasue oil is a very cold thick gunk when cold. You would want to be running an oil in your area like 5W40 synthetic Rotella (Shell). If your oil light is staying on when you crank, and going out after the other warning lights have reset, that could be an indicator.

4. An exhaust leak can be found with a number methods. One is using a listening stick, long screw driver, or mechanic's stethoscope pressed to your ear and the suspect area to hear above the regular engine noise. Another is to do a Seafoam induction cleaning, see tech area, and the resulting smoke will come out of the exhaust leaks as well. Another can be done with truck off, shove a shop vac output (low air pressure) with a rag in the tail pipe. Friend who smokes blows smoke in the engine area and look for air blowing it around, like around manifolds and the joint to the down pipe. You can usually see a black smear at the joint where the leak is happening.

5. Could be good old engine oil sludge, left behind by a previous owner who ran regular gas, did an oil change once a year whether it needed it or not, and always got 10W30 elcheapo oil at the quicklube shop.

 

You need to put more of your energy into getting the the cause of this noise. If it is internal engine noise, you are causing damage everytime you start the engine, hence quit starting it till you or a goo shop can locate or fix the problem.
What oil, weight and filter are you running?

 

In the mornings when its colder than usual I always have had a small quick tap sound when first cranking the engine over, but it happens only the once and then is gone. I hate the sounds, but have not attributed it to anything dire thus far. No codes or anything just a quick tap upon initial start up, and then gone.

 

The previous owner did use regular oil.
HG, timming chain cover seal and oil pan gaskets were done around 15k miles ago. When I got the car, PSP was shot and only thing that I could hear was power steering pump noise, now every thing else is coming to light after replacing the PSP.

I am almost done with the whole 60K service except for the drive shaft and plugs/wires.

I did flush the engine with gunk and am using rotella 5-40 synthetic oil.
After around 500miles engine oil still looks fairly clean, barely visible on the stick. so I might or might not have any gunk in the engine.

The loud ticking/knoking is very loud until the RPM starts dropping, at that time the sounds gets better like after a minute or less.

oil sign goes out relatively quickly. I recently run out of gas and I noted that the light was going out during cranking even the motor did not start, but I will check the oil pressure, since i also have the intermittent ticking when the engine is warm.

In addition to the knoking there is also a whining sound when the engine is cold and a similar type of whining sound when I drive at high way speed. I don't know if that is just regular engine noise, since it runs at high RPM or may be some thing else.

Just after the PSP replacement I heard an intermittent squeeking type sound comming from the front of the engine where the SB is. It sounded almost as if you have to move some rusty/stuck part, this was not continous and I do not have it anymore. I don't know if this can point to anything.


I don't have a shop vac, but I will do the induction again to see if I have any leak. I did the induction around 500 miles ago, I hope the second induction will not cause any damage.

Thanks

 

I am looking for a local LR specialist other than the dealer, I did take it to my local indy, but the engine was warm at that point and he said every thing sounds normal. I still have few other things to take care of including the drive shaft, front axle seal (leaking slightly), oil filter housing O-ring (leaking pretty good) and transfer care leak at a very odd place.
So I am definitely not ignoring things, I hope I am not reading too much into things either.

 

An exhaust leak is usually at a "repetition rate" or "beat" of the multiple cyclinders on that side where the leak is, and an rod knock would be a slower thuunk-thunk-thunk.

I would concentrate on the oil pressure first.

An exhaust leak won't kill your engine, but an oil problem can be game over.

 

[quote=Savannah Buzz;297051]1. Two fans, one is mechanical, driven by the serpantine belt, and has a fan clutch that simply makes it run at low power or higher power, but never "no power". This type of clutch is called a viscous clutch, and is fully engaged when parked overnight and cold, becasue the silicone liquid inside has all pooled to one side. When engine cranks the fan will "roar" until clutch fluid warms up and spreads out by rotating force, and clutch backs off engagement to lower power option. You could remove the serpantine belt and crank the truck cold, to eliminate the fan motion. OK to run without fan as long as you don't stay parked or stopped for more than 3-5 minutes while testing. Some owners in the border states (Canadian border) run with no fan in the winter to warm up truck faster, just watch temp gauge when you are sitting for long periods).[quote]

I didn't know that the engine could start without the serpantine belt. When I replace my 96 Disco's PSP, i had the SB routed wrong and the engine was cranking but not starting

 

It is more like a repetition beat, but I will take your advise on the oil pressure check. You know your staff and I am glad you'r here.
I will get a pressure gauge, reading through the forum, you just unplug the factory wire and connect the new gauge to check the pressure. Is this right?

 

I think everyone is missing the obvious first assumption... lifters. I had the same cold knock. 101k miles. Lifters were so worn out they were dished inwards, flat, and some weren't even spinning in their bores and were wearing one way. It would just take a couple minutes for the air to bleed out of one if them. New lifters cured it. Been good ever since. Just a thought.